The distribution of dextran macromolecules in the glomeruli of normal and nephrotoxic rats

The incorporation of intravenously injected dextran molecules (molecular weight 500,000 & 2,000,000) by the glomeruli of laboratory rats was studied by electron microscopy. In normal rats some dextran molecules were observed 12 minutes after injection in vesicles and invaginations of both endothelial and mesangial cells. Rats with nephrotoxic serum nephritis showed extensive separation of endothelial cells from the glomerular basement membrane. These subendothelial spaces contained irregular granular material, cytoplasmic extensions of mesangial cells and, in animals injected with dextran, dense accumulations of dextran molecules. There was no apparent difference in distribution of the two test samples of dextran. These findings demonstrated the involvement of both endothelial and mesangial cells in the glomerular localization of circulating material and indicated that immunologically inactive macromolecules can be incorporated into subendothelial deposits following immunological injury to the glomerulus.